Breaking down ALD Investigating pathomechanisms using hiPSC-derived CNS models

Adrenoleukodystrophy (ALD) is an X-linked peroxisomal neurometabolic disorder caused by pathogenic variants in the ABCD1 gene, resulting in impaired peroxisomal ß-oxidation and accumulation of very long-chain fatty acids (VLCFA). ALD clinical presentation is heterogeneous and unpredictable, including progressive spinal cord axonal degeneration, adrenal insufficiency, and leukodystrophy. Although VLCFA accumulation represents a clear biochemical hallmark of ALD, the cellular and molecular mechanisms linking this metabolic defect to the diverse neurological outcomes remain poorly understood. This thesis dissects ALD pathomechanisms using human induced pluripotent stem cell (hiPSC)-derived central nervous system (CNS) models, with an emphasis on lipid metabolism and neurodevelopment. First, we generated hiPSC-derived astrocytes to explore the cell-autonomous consequences of ABCD1 deficiency. ALD hiPSC-derived astrocytes recapitulate the biochemical hallmarks of ALD, showing impaired peroxisomal ß-oxidation and VLCFA accumulation next to an altered lipid profile. These lipid alterations were associated with a reduced capacity of astrocytes to support neurons in co-cultures, highlighting the critical role of astrocytes in neuronal health. Building on these findings, we generated hiPSC-derived cortical and spinal cord organoids. By mapping the lipid profile across organoid development, we observed a dynamic lipid landscape and its alterations in disease. ALD hiPSC-derived organoids displayed lipid alterations throughout the differentiation, including enrichment in VLCFA lipid species and reductions in brain-relevant lipids in cortical organoids. Integrating lipidomic data with transcriptomic and proteomic analyses revealed a consistent dysregulation of pathways involved in lipid metabolism. Collectively, these findings establish hiPSC-derived CNS models as a versatile platform to investigate ALD pathomechanisms.